1. Field of the Invention
The present invention relates to racking systems for cargo vehicles, such as box type trucks, and more particularly, to such systems that include internal shelves and shelf supporting structures.
2. Description of Related Art
Although a large variety of box truck designs exist, they all include the common features of large interior space defined by the sidewalls, front and back walls, top wall, and floor. The steel truck mainframe supports the flooring, which can include a wooden or metal platform secured to the main frame. The floor is normally bowed from front to rear in order to compensate for and provide some flexibility for heavy loads carried within the cargo area. The sidewalls and ceiling or roof usually comprise material with little load bearing capability, such as fiberglass, plywood, thin sheet metal, etc. The primary cargo load bearing structure for trucks of this type include the flooring and main frame. For many designs, metal steel or aluminum bars mounted at the box corners and along the edges of the box for the purpose of transferring and carrying forces outward and downward to the main frame. Also, the side walls may be corrugated with vertically extending channels to purportedly strengthen the sidewalls, or a portion of the sidewall may be fitted with a series of longitudinally spaced vertically extending channel members riveted to the inside or outside of the side walls.
It is known that these box trucks have great utility, particularly for delivery companies that pick up, haul, and deliver a great number or variety of packages potentially of varying size, shape, and weight. There is a present need in this industry for box trucks that include racking or shelving systems that provide two or three levels of shelves within the cargo area, in which the shelves can be easily and reliably rotated between a near vertical stored position and a horizontal utility position.
One known attempt at such a system included an elongated piano hinge assembly having one stationary horizontal bar part bolted or riveted to the inside surface of the sidewalls. In this conventional system, metal shelving connects to the other or rotating part of the hinge assembly. The shelving rotates downward to a storage position and rotates to a horizontal position for use.
Technical difficulties with this system included damage to the sidewalls resulting primarily from the static and dynamic shelf and cargo weight as well as the vibrations imparted to the connection points where the hinge member is riveted to the sidewalls. Another disadvantage relates to the permanent fixed position of the piano hinge, which prevents vertical adjustment of the shelving after initial installation. That is, while a shelf may be moved into either a downward storage position or a flat in-use position, the spacing between shelves is not adjustable after installation.